Various parameters related to a living body fluctuate according to a rhythm with a specific cycle called biological rhythm. A typical example of a technique which analyzes the biological rhythm is the CONSINOR method disclosed in Non-Patent Literature 1. The CONSINOR method applies time series data to a cosine curve using a least square technique, and sets a cycle, amplitude, and level of the cosine curve as characteristics of the biological rhythm. The CONSINOR method is an effective analytic method, when the time series data exhibits sinusoidal changes.
The disturbance of the biological rhythm is said to have a crucial impact on health conditions of a living body. For this reason, studies on what kind of disorders the disturbance of the biological rhythm exerts on the body have been conducted (for example, Non-Patent Literature 2). In Non-Patent Literature 2, effects of the disturbance of the biological rhythm on the body are investigated by examining a piece of tissue of a portion called suprachiasmatic nucleus (SCN: SupraChiasmatic Nucleus) of the brain of a mouse.